Cancer is the leading cause of disease-related deaths among children 1 to 14 years of age, and leukemia is the most common malignancy in children. Every year, approximately 20% of children diagnosed with acute leukemia are diagnosed with acute myelogenous leukemia (AML). Though AML constitutes a smaller percentage of childhood leukemia than acute lymphoblastic leukemia (ALL), AML carries an inferior prognosis. In contrast to the improvements in ALL cure rates over the past 20-30 years (now ~80% overall survival), the overall survival for pediatric AML is 50-60% and the chemotherapy is intensive with frequent required hospitalization. Relapsed AML carries survival rate with chemotherapy alone of 20% to 30%. This suboptimal prognosis demonstrates the need for more research into improvement in the outcome of pediatric AML. Furthermore, current chemotherapeutics produce significant short-term and long-term toxicities. Thus, new therapies are needed to continue to improve efficacy and decrease treatment related toxicity. My lab studies Mer and Axl, receptor tyrosine kinase proteins abnormally expressed and activated in childhood acute myeloid leukemia. Mer and Axl have multiple functions pertaining to cell cycling, survival, and proliferation. In the current grant proposal, we will evaluate leukemia cell death after inhibition of Mer and/or Axl in childhood myeloid leukemia cells using novel biologic inhibitors developed in my lab. We will also provide additional evidence in cell culture for our exciting preliminary results that Mer inhibition makes leukemia cells more sensitive to standard leukemia chemotherapy drugs. Additionally, Mer and inhibition will be tested for efficacy in mouse animal models of human leukemia. These experiments will help establish the related Mer and Axl receptors as novel targets for childhood AML therapy. The proposed studies will also potentially provide pediatric oncologists with a highly effective and much less toxic alternative to the currently used chemotherapy drugs in the treatment of childhood AML.